Cutting tools employed for use in precision machine tools are typically manufactured from high strength steels and are adapted to be rigidly mounted in order to eliminate cutting error due to vibration or deflection of the cutting tool. Since cutting tools wear or grow dull after a period of use, such tools are normally manufactured in the form of a cutting tool insert which is removably mounted in a tool holder. For example, U.S. Pat. Nos. 3,238,600 and 3,310,859 disclose a cutting tool assembly in which a cutting tool insert having a plurality of cutting edges is releasably held by a cutting tool holder. The cutting tool insert has an aperture therethrough for receiving a retaining screw which is threadably received in the holder and locks the insert in wedged relationship between a pair of seats defined in one side of the holder.
The cutting tool holder disclosed in the patents mentioned above is relatively massive and is therefore costly from a production standpoint. This type of holder is also relatively expensive to produce since cutout areas must be machined in the side of the holder in order to produce the insert seats. This prior art tool holder was particularly undesirable from the standpoint that the retaining screw for holding the insert in the holder had to be completely removed in order to remove or index the insert so as to expose a fresh cutting edge. The necessity for completely removing the retaining screw naturally introduced delays in the machining process thereby unnecessarily increasing the production costs of the workpiece being machined. This problem is aggrevated by the fact that tool holders are often surrounded by other operating parts of the machine, or by the workpiece itself; under these circumstances, the machine operator may have access to the tool holder but may not have visual contact therewith during the removal or indexing of the cutting insert. Thus, the machine operator is working "blind" on the tool holder; this further contributes to machine downtime, and increases the risk that the operator may accidentally drop or lose certain components of the holder during removal or indexing of the cutting insert.
Known prior art tool holders of the type described above are not provided with means for breaking a chip as it is cut from a workpiece by the cutting insert. Although chip breakers are old per se in the art, these devices are normally retrofit to tool holders, thereby adding to the cost of the cutting tool and complicating its overall design.
Accordingly, it is a primary object of the present invention to provide an improved cutting tool which includes a simple tool holder which is economical to manufacture but yet which allows rapid, reliable removal and/or indexing of a cutting insert held thereby.
Another object of the invention is to provide a cutting tool holder as described above which reduces the number of component parts required to reliably hold a cutting insert, and which reduces the overall amount of material required to manufacture the same.
A further object of the invention is to provide a cutting tool holder of the type described above which provides a chip breaker formed integral therewith which is highly effective in breaking chips as they are cut from a workpiece.
A still further object of the invention is to provide a holder as described above which provides selflocating and positive seating of the cutting insert in the holder, even under blind installation conditions.
These and further object of the invention will be made clear or will become apparent during the course of the following description of a preferred embodiment of the invention.